Vellus Hair

Vellus hair refers to the very fine, short hairs that are present across much of the human body. They are typically less than 2 mm in length, lightly pigmented or non-pigmented, and produced by smaller, thinner hair follicles; unlike terminal hair, vellus hair has a short growth phase and contributes little to visible hair density.

Clinically, vellus hair is important because changes in its appearance or proportion relative to terminal hair can signal underlying processes: for example, hormonal influences can cause vellus hairs to become thicker and pigmented (conversion to terminal hair), while hair follicle miniaturization in conditions like androgenetic alopecia often leads to the replacement of terminal hairs with finer vellus-like hairs. Understanding these patterns helps clinicians assess hair loss, hirsutism, and responses to medical or surgical treatments aimed at restoring thicker terminal hair.